The invention relates to a method of detecting at least one predetermined shift position of a vehicle transmission among a plurality of different shift positions corresponding to different rotary transfer ratios between an input shaft and an output shaft. It further relates to a control device, to a vehicle transmission, as well as the use of the method, the use of the control device, and the use of the vehicle transmission. In addition, the invention also relates to a method of detecting a position change in relation to a reference position of a vehicle transmission.
A transmission in the present context means a device that can be shifted into different states, by an either stepwise or continuous variation, to generate different rotary transfer ratios between two shafts. The transmission is configured as a gear-changing transmission or a cone-pulley transmission, or other appropriate mechanism. The shift processes of the transmission can be controlled automatically or manually, or in a partially automatic mode, or in an automated mode that permits manual intervention by the driver. A transmission in the sense of the present invention can be configured so that shifts from one gear ratio to another cause an interruption in vehicle traction, or it can be configured to perform shifts without interrupting traction.
With preference, the transmission is configured as an automatic transmission which, in the context of the present invention, means a transmission that shifts without interrupting traction. With special preference, however, the transmission is configured as an automated shift transmission, a term which is used in particular for a transmission in which the control of the shift process is automated but causes an interruption in vehicle traction.
Transmissions as well as operating methods for transmissions belong to the known state of the art.
In a manual transmission, the gear shifts are performed manually by the driver. In principle, the driver is free to shift arbitrarily from any gear into any other gear. The driver chooses when to shift gears and which gear to shift into, based on certain criteria. The driver will decide to shift gears particularly in response to the sound of the engine and depending on which of the gears is currently engaged.
Errors in recognizing which gear is currently engaged, errors of shifting into an other than the intended gear, judgment errors about the need to shift gears, or other mistakes can cause damage to a transmission or can stall the engine of a vehicle. This kind of situation can occur, for example, in a vehicle coasting downhill with the transmission set to the neutral position, if the driver's foot is on the gas pedal so that the engine runs at a high rpm rate but the driver erroneously believes the transmission to be in first gear and therefore shifts into second gear.
Also known are automated shift transmissions in which the shifts are actuated by two electric motors. The electric motors apply a force to a shifter finger. The shifter finger moves in a pattern that consists of a selector track (also called neutral track) and shift tracks branching off from the selector track. The first of the electric motors moves the shifter finger in the direction of the shift tracks which terminate at the different gear positions, while the second of the electric motors moves the shifter finger in the direction of the selector track where the transmission is in the neutral state.
The shifter finger position is monitored by displacement sensors which are arranged at the electric motors and work according to an incremental detection principle.
The shifter finger is controlled by the electric motors dependent on the position values generated by the incremental sensors.
Automated shift transmissions of the foregoing description provide a satisfactory level of shifting and driving comfort and an economical way of operating a vehicle.
However, there have been incidents where gear shifts where performed incorrectly by transmissions of this type. Incorrect gear shifts are detrimental to the driving comfort in a vehicle with an automated shift transmission and will shorten the life of the transmission.